During this time, she has been a full time working member of the family and carried out many royal duties.
Her choice of jewellery could represent the growing importance of her role as she is married to the future King.
It could also show her growing confidence in her role in the family, the jewellery expert suggested.
How did Kate Middleton become a royal?
Kate Middleton, or Catherine, Duchess of Cambridge, was born on 9 January 1982 at the Royal Berkshire Hospital, Reading, England.
She was born to Michael and Carole Middleton, a former flight dispatcher and air hostess. The couple founded a party supplies company, Party Pieces, in 1987 – now estimated to be worth £30 million.
Kate has a younger sister Pippa Matthews, 34, and a younger brother James Middleton, 31.
Kate and her family moved to Amman, Jordan, in 1984, where the future Duchess was educated at an English-speaking nursery school.
After moving back to Berkshire the family sent Kate to private school, St Andrews School. She went on to briefly study at Downe House before moving onto Marlborough College where she boarded.
For university the young Kate attended the University of St Andrews in Fife, Scotland. Here she was awarded an undergraduate MA (2:1 Hons) in history of art.
Relationship with Prince William
Kate met Prince William when they were both studying at St Andrews, and both living in St Salvator’s Hall. Famously, William reportedly took a fancy to Kate after she wore a see-through dress during a fashion show.
In 2003 the couple began dating and lived together during their second year of university.
The couple split in April 2007, however, in October they were back together.
Prince William proposed to Kate Middleton with his late mother Princess Diana’s engagement ring in October 2010. The couple were holidaying in Kenya at the time.
On 29 April 2011 they married at Westminster Abbey with a whopping 26 million watching the event live.
Kate wore an Alexander McQueen dress worth a reported £250,000 on the big day.
Kate assumed the title “Her Royal Highness The Duchess of Cambridge” and also become the Duchess of Cambridge on the day.